Darwin's Four Postulates

Charles Darwin Theory of Evolution by Isabel Gutierrez

Darwin's Four Postulates

Charles Darwin Theory of Evolution by Isabel Gutierrez

Graphs and Statistics

Variation and Heritage

1. Individuals are variable -- phenotypes vary within a population. Two types of variations: continuous variations or discontinuous variations. Variations can be useful, harmful or neutral.

2. Some variations are passed down through generations -- offspring of successful species inherit the successful phenotypes.

Offspring Survival

3. More offspring are produced than can survive -- Species reproduce at large rates, but not all of them survive. Although species reproduce geometrically, food only increases arithmetically. This means that there’s not enough for all of the species of organisms that are being reproduced.

Natural Selection

4. Survival and reproduction are not random -- natural selection acts as a restrictive force, allowing only the most biologically fit species to survive. This means that nature chooses the organisms that are useful to provide future reproduction of the species. These organisms are supposed to be those who are the most fit to survive.

Examples

Phenotype Variation

In the finch example that was provided, their phenotypes changed according to their environments. In this example, the change was useful, and therefore, continuous. This means that the new phenotype was passed down through generations to create new species of finches with different beaks.

More Offspring Are Produced Than Can Survive

Sea turtles, for example, lay way more eggs than the number of turtles that reach the ocean. This is so at least some of them survive and are able to keep the species alive.

Survival Is Not Random

Polar bears, for example, were able to survive because of their hunting and camouflage abilities.

Phenotype Variation

In the finch example that was provided, their phenotypes changed according to their environments. In this example, the change was useful, and therefore, continuous. This means that the new phenotype was passed down through generations to create new species of finches with different beaks.

More Offspring Are Produced Than Can Survive

Sea turtles, for example, lay way more eggs than the number of turtles that reach the ocean. This is so at least some of them survive and are able to keep the species alive.

Survival Is Not Random

Polar bears, for example, were able to survive because of their hunting and camouflage abilities.